1. Field of the Invention
The invention relates to railroads generally, and more particularly to automatic control of trains.
2. Discussion of the Background
Controlling the movement of trains in a modern environment both in a train yard and on the main line is a complex process. Collisions with other trains must be avoided and regulations in areas such as grade crossings must be complied with. The pressure to increase the performance of rail systems, in terms of speed, reliability and safety, has led to many proposals to automate various aspects of train operation.
One traditional method for controlling trains is known as track warrant control. This method is most often used in areas of dark territory (track that does not include a wayside signaling system). Simply put, a track warrant is permission to occupy a given section of track, i.e., a block. The traditional track warrant control method, which is defined in the General Code of Operational Rules, involves “written” verbal orders which may be modified or rescinded by communication over a radio with a dispatcher. In the system, a dispatcher gives a train or a maintenance crew verbal authority (a warrant) to occupy a portion of main line track between named locations (e.g., mile markers, switches, stations, or other points). In addition to specifying certain track sections, track warrants can specify speed limits, direction, time limits, and whether to clear the main line (e.g., by entering a secondary track such as a siding) and/or any other section of track (sidings, yards secondary track, etc . . . ). There is a complicated and time consuming procedure by which track warrants are issued which involves the train conductor or engineer reading back the warrant to the dispatcher before the warrant goes into effect. One important disadvantage to this system is that it relies on human beings, both to communicate the warrant properly and to ensure that the warrant is complied with. The system is thus subject to errors which can be disastrous.
Some systems, such as the Track Warrant Control System sold by RDC (Railroad Development Corporation), have automated some of the track warrant control method, such as by sending the warrant to the train via a computer system. Another system, Automatic Block Signaling (ABS), provides for automated wayside signaling of block status and authority to enter or occupy a block. In this system, track warrants may overlap and the conductor or engineer uses the automatic wayside signals to determine when and how to proceed in a given block. Again, human beings are involved and errors are possible.
In another system known as Cab Signal, a display is provided in the cab for the engineer/conductor. This display basically displays wayside signals to the engineer/conductor and forces the engineer/conductor to acknowledge signals that are more restrictive than the current signal. However, the Cab Signal system does not force the engineer/conductor to obey the more restrictive signal. Thus, an engineer/conductor may be forced to acknowledge a signal that reduces the maximum speed from 20 m.p.h. to 10 m.p.h., but the train will not be forced to slow to 10 m.p.h.; rather, the engineer/conductor must take action to slow the train. Once again, the potential for error exists.
A second traditional system known as Centralized Traffic Control (CTC) allows a dispatcher to control movement of trains by controlling track switches and wayside signals from a central dispatch office. In these systems, there is no direct communication with the locomotive cab; rather, the dispatcher sends commands to switches and wayside signals and receives feedback from them. Again, the wayside signal indicate authority to occupy a block or to proceed to the next block. These systems still require a human operation to control movement of the train in accordance with wayside signals. Updated CTC systems such as the Radio Actuated Code System from Harmon Electronics integrate differential GPS (global positioning system) technology and other technology into these systems, but they are still subject to human error.
Some efforts at automation have been made. For example, a rudimentary system known as Automatic Train Stop (ATS), sold by Union Switch and Signal Inc., functions by means of a mechanical contact between a wayside trip arm and a brake emergency trip switch or cock mounted to the car. If the wayside signal is in a stop condition and the train passes the signal, the wayside trip arm activates the emergency brake switch, thereby initiating an emergency brake operation. One problem with a rudimentary system such as this is that the braking operation is not started until the train passes the wayside switch, which means the train will not stop until some point after the switch. Thus, the system will not prevent a collision with an object that is close to the wayside signal.
Another problem with all of the foregoing system is that they require wayside signaling. These wayside signal systems are expensive to maintain and operate. Doing away with wayside signaling has been desired by train operators for many years.
The foregoing concerns have led to more automated systems. For example, in the Automatic Train Control (ATC) system, train location information, speed information, and train control information are continually exchanged between a train cab and computerized wayside controllers in real time (in some systems, track rails are used to carry this information). In this system, it is not necessary for a conductor or engineer to look for wayside signals. If a wayside signal is missed by a conductor or engineer, or conditions change after the wayside signal is passed, the information is available to the conductor or engineer in the cab. Some ATC systems automatically apply the brakes if a stop signal is passed. As discussed above in connection with the ABS system, such after-the-fact braking systems may not prevent collision with an object located in close proximity to a wayside signal. Other systems, such as the Advanced Train Control System proposed by Rockwell International, will automatically apply the brakes if a track warrant is about to be exceeded.
An advanced version of the ATC system, referred to as the Advanced Automated Train Control (AATC) system, is offered in combination with an Automatic Train Operation (ATO) system by General Electric Transportation Systems to fully automate movement of trains.
In at least one New Jersey Transit system, the ATC system has been combined with a Positive Train Stop (PTS) system. The PTS system uses transponders along the tracks and on-board receivers to supplement the ATC system. PTS is an intelligent system that anticipates signaling and will stop or slow the train automatically without operator input. For example, as discussed above, while ATC will stop the train automatically if the train runs through a stop signal, PTS will stop the train before actually going through a stop signal. In addition, the PTS system allows for “civil-speed” and “temporary construction” speed restrictions. The term Advanced Speed Enforcement System (ASES) is used when ATC and PTS are combined.
Another system sold by Harmon Industries and referred to as Ultracab also involves an ATC system that will automatically stop a train before going through a stop signal. However, one drawback to both the PTS and Ultracab systems is that they assume the worst case scenario when automatically stopping a train, i.e, they employ a fixed braking curve. Thus, for example, when these system detect an upcoming stop signal, they will apply the brakes at a distance that assumes that the train is traveling downhill on the most steeply graded section of track, and that the train is at the maximum weight. This worst-case assumption/fixed braking curve makes such systems inefficient.
In more recent years a next generation train control system referred to as Positive Train Control, or PTC, has been proposed. A number of companies have proposed different systems that function in different ways to implement PTC systems. For example, GE Transportation Systems markets a product referred to as the Incremental Train Control System (ITCS) and GE Harris Railway Electronics markets a version referred to as Precision Train Control. The Federal Railroad Administration (FRA) has stated that from the point of view of safety objectives, a PTC system needs to achieve the following core functions with a high degree of reliability and effectiveness: prevent train-to-train collisions (positive train separation); enforce speed restrictions, including civil engineering restrictions and temporary slow orders; and provide protection of roadway workers and their equipment operating under specific authorities.
In addition to the performance and safety issues discussed above, vandalism is becoming an increasing concern of train operators. One form of vandalism is the unauthorized moving of trains. Much like some people ‘borrow’ a car for joyriding, some will joyride on trains. Unlike cars, a key is often not required to “start” a train. While a locomotive cab may be locked, it is fairly easy to break the lock and enter the cab, at which point a train can be made to move. Unauthorized movement of a train, whether on a main line, in a train yard, or on some other section of track, can cause much damage even if a stop signal is not violated.
Another vandalism problem is the uncoupling of trains while the trains are at rest. Ordinarily, but not necessarily, if a car becomes detached from a train due to some mechanical failure, the loss in pressure in the brake lines will cause the trains to immediately stop. However, if a vandal disconnects a car from a train while in the yard and properly shuts the air valve for the brake line to the remaining cars, this protection does not work. When a train has many cars, a conductor or engineer may not notice that the car has been disconnected. In this case, the car left behind may cause a collision with an oncoming train or may just roll away and then cause a collision. This problem is partially solved by the use of known end-of-train devices that include motion sensors that allow a conductor or engineer in the locomotive cab to verify that the last car is in motion. However, the motion sensors sometimes break or give false readings and, under certain circumstances described more fully herein, may mislead a conductor or engineer even when working properly.
What is needed is a method and system that allows for the efficient and safe operation of a railroad while mitigating the effects of vandalism.